1. Field of the Invention
The present invention relates to components for use in plasma process chambers, and more particularly to components for use in plasma process chambers that have superior erosion resistance.
2. Brief Description of the Background Art
The semiconductor industry relies on high throughput, single substrate processing reactors, which can be used for a variety of different plasma processes including plasma-enhanced CVD (PECVD) and plasma-assisted etching.
In some process chamber environments, for example, halogen containing high-density plasma-etching chamber environments, conditions are highly aggressive, causing erosion of various chamber components, including chamber walls, liners, process kits and dielectric windows. This is particularly true of high-density fluorine-containing plasma-etching environments, which are frequently used in connection with dielectric etching processes.
Some process chamber components (for example, chamber walls and liners for inductively coupled plasma reactors) are made from electrically conductive materials. Such conductive components are commonly made from aluminum and anodized aluminum. Unfortunately, in aggressive process chamber environments like those described above, significant aluminum erosion occurs. This erosion results in the formation of aluminum particles and contaminant compounds that can cause damage to the substrate being processed. It is known in the art to address this problem by coating these materials with a layer of yttria (i.e., yttrium oxide, which is typically represented by the formula Y2O3) or with a coating of YAG (i.e., yttrium aluminum garnet, which is a solid solution of aluminum oxide and yttrium oxide and is typically represented by the formula Y3Al5O12). However, these coatings, while being resistant to plasma erosion, frequently suffer from spalling and cracking.
Other process chamber components are required to be electrically insulating in nature. For example, in inductively coupled plasma process chambers, a plasma is generated in a reactive gas inside the chamber using an inductive coil that is placed outside the chamber. For effective coupling of power from the inductive coil to the gas inside, it is necessary to fabricate the chamber component that is positioned between the inductive coil and the chamber interior (for example, the chamber roof) from an electrical insulator such as a ceramic or quartz. The material most commonly used to fabricate such “dielectric windows” is aluminum oxide (alumina). However, in aggressive chamber environments like those previously described, etching of the alumina can occur, leading to the formation of particles and contaminating compounds. Chamber roofs made of yttrium-aluminum oxide (e.g., yttrium aluminum garnet) are known and hold up much better than alumina in terms of erosion. However, yttrium aluminum garnet is relatively more expensive than alumina, and it is also typically more brittle.